The only one that had any personality or character growth to him at all was Wrex. Even Garrus, everyone's new favorite circa ME2, was pretty terrible in ME1. Even Tali was nothing more than a vehicle for the Quarian race.

ME2 had better characters. The returning characters were fleshed out nicely. The other ones had actual conflict in their lives on a personal level. Morlan was fantastic. Jack was interesting, one you got past her ridiculous design. Garrus' vigilante leanings were more interesting than his gruff-and-angry schpeel. Legion was fascinating. Zaeed, who I held to a lesser standard because he wasn't quite a full party member, had the gruff veteran soldier thing down to a T. Hell, Miranda as a character annoyed the crap out of me, but I still consider her a success because she annoyed me the way a real person might have.

ME1 had vastly superior story, which arguably allowed mediocre characters to shine beyond what they really deserved. Only Wrex and Joker from the first game were any good.

My biggest complaint about ME2 was that the story felt formulaic. It was very obviously disjointed in a series of modular pieces, each one of which followed a clear and predictable pattern - one that the game didn't even try to hide from us.